[nat64] link libanl library to the otbr-agent module in Android.mk (#1531)
[nat64] link libanl library to the otbr-agent module in Android.mk (#1531)

This commit links the libanl library to the otbr-agent module in
Android.mk. This library is needed for properly referencing the
getaddrinfo_a function in openthread/src/posix/platform/netif.cpp
openthread/ot-br-posix,openthread/borderrouter,openthread/ot-br-posix,openthread/borderrouter,openthread/borderrouter,openthread/borderrouter,openthread/borderrouter,openthread/ot-br-posix,openthread/ot-br-posix,openthread/ot-br-posix,openthread/borderrouter,openthread/ot-br-posix